Pacific Decadal Oscillation
Understanding the Pacific Decadal Oscillation (PDO)
At our farmer meetings, we’re often asked about longterm forcasts and the impacts on current weather patterns—and ultimately, your operation. This page offers a simple overview to help explain what the PDO is and why it matters to agriculture.
The PDO is a long-term climate pattern involving sea surface temperature anomalies in the Pacific Ocean. It operates in multi-decade phases, typically lasting 10 to 30 years.
In the positive phase, sea surface temperatures rise along the eastern Pacific (near the Americas), while the western Pacific cools slightly.
In the negative phase, the pattern reverses—cooler temperatures dominate the eastern Pacific and warmer waters shift westward.
In recent years, we’ve been in a negative PDO phase, which can influence regional rainfall and drought conditions—making it an important factor when planning your PRF coverage.
Positive PDO
When sea surface temperatures are abnormally cool in the interior North Pacific and warm along the Pacific Coast, and when sea level pressures are below average over the North Pacific, the PDO has a positive value. The waters along the equator are much warmer. This tends to create more El Nino-like weather patterns across the United States. See map below.
El Nino Weather Pattern
A Negative PDO
A negative PDO is the exact opposite of a positive one. When we are in a negative phase we have cooler waters on the west coast of the United States and along the equator. It looks and acts a lot like a La Nina a weather pattern. We are currently in a negative PDO.
La Nina Weather Pattern
Below you can easily see the differences between the positive and negative phases of the PDO. Part (C) Is a timeline that illustrates how the PDO goes back and forth between Positive (+) and Negative (-) PDO. Today we are in a negative PDO, it is a -1.98 which is strong. This means that the weather is more likely to resemble weather patterns that are normal to a La Nina.